The attack was taken so seriously that it was raised with Mr McGuinness by Barack Obama at a private meeting in the White House during the St Patrick’s Day celebrations in Washington.

The issue was raised alongside other security concerns, like the flag protests.

The incident had been reported back to Washington by the State Department and passed on to the President as part of his pre-visit briefing.

Mr Obama obviously has a particular concern about security issues here because he will be visiting Northern Ireland alongside other world leaders for the G8 meeting in June. Vice President Joe Biden is planning a parallel visit here.

Nobody was injured in the attack in Londonderry, in which the family home was drenched in black paint. The significance is that dissident supporters felt confident to approach the house of a senior politician and attack it, even with paint.

It shows that they are prepared to go beyond verbal threats.

A Sinn Fein spokesman declined to confirm or deny what had happened. “We don’t comment on issues of personal security,” he said.

However, on March 7 Mr McGuinness did comment on a death threat he had received as a result of speaking out strongly against an attempt to mortar bomb police headquarters in the city. One hundred families in the Letterkenny and Lonemore Road areas were evacuated from their homes until it was defused.

“I was visited at home by the PSNI who informed me of a real and active threat against me from a dissident group in Derry. They linked the threat to my condemnation of the recent attempted mortar attack in the city and other remarks made in support of the PSNI,” he said at the time.

In comments that could equally well have applied to the attack on his home, Mr McGuinness added: “It says much about the mentality of those controlling groups like the one behind the threat that in their warped logic threatening Irish republicans and their families somehow advances the cause of Irish reunification.

“There are times when in political leadership staying silent is not an option, and I will not be silenced by threats like this. I will defend the peace process from attack from whatever quarter, be it these groups or the loyalist flag protesters over recent months.”

Mr McGuinness added at the time: “I am also very sure that it is the path shared by republicans across this island genuinely interested in building a new agreed Ireland, republicans who put Ireland before ego, criminality and self-gain.”

The paint-bombing incident was not reported to the police, according to a PSNI spokesman.

This Sunday Mr McGuinness is expected to strike a similar note of reconciliation and confidence in the peace process when he addresses the main republican Easter commemoration in Dublin’s Garden of Remembrance. He may also renew his offer to talk to the dissidents about their concerns.

Analysis: Proof we are living in whole new era

By Liam Clarke

Another peace process Rubicon was crossed when Martin McGuiness sought no publicity for the attack on his home, and no retaliation followed for those thought to be involved.

In the past threatening a senior republican like Martin McGuinness and attacking his family home, even with paint, would have brought a swift response from the IRA.

The culprits would have been exiled from Derry or worse. Their own homes would have been at risk. Those days are now gone — the once heavy hand of the Provos did not come down with crushing force, as would once have been expected.

That is good news. It is further evidence the peace process is now irreversible, at least for Mr McGuinness’s generation of leadership which led the republican movement through the Troubles and the peace process.

Living, as he does, in an area where the dissident groups have support, he has shown considerable courage in speaking out against them. When he tells them that their violent struggle is futile and that it is contrary to the interests of the Irish people, he is speaking from the heart and from experience.

Violence is also a sign of weakness — a fatal flaw which will limit the growth of these groups. Sinn Fein never grew beyond an activist band, sustained by a backbone of prisoners’ relatives, while the IRA attacked nationalist politicians like John Hume.

Peace and promise of peace played better, eventually making Sinn Fein a potent force.

The dissidents can learn from this. They may demonise Mr McGuinness as the IRA demonised Mr Hume in an earlier era. But they cannot destroy his ideas, his analysis or his example by force, threat or ridicule.

The IRA campaign and the subsequent peace process offer lessons for republicans which Martin McGuinness personifies. Only fools could ignore them.